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February 28th, 2010 at 3:00 pm

Auger Electron Spectroscopy

DESCRIPTION OF TECHNIQUE

Auger Electron Spectroscopy (AES) provides information on the chemical composition of the outer material that includes a solid surface or interface. The main advantages of AES over other methods of surface analysis are excellent spatial resolution (<1 micron), the sensitivity of the surface (~ 20 aa), and detection of light elements. Detection limits for most elements ranged from approximately 0.01-0.1% a.

AES uses a primary beam of electrons to excite the sample surface. When an inner-shell electron is ejected from an atom of the sample through interaction with a primary electron, an electron from an outer shell fills the vacancy. To compensate for the change of energy from this transition, an Auger electron or X-rays is emitted. For light elements, the probability is greater for the issuance of an Auger electron, which represents the light element sensitivity of this technique.

The energy emitted Auger electron is characteristic of the element from which it was issued. The detection and energy analysis of Auger electrons emitted produces an Auger electron energy spectrum against the relative abundance of electrons. Peaks in the spectrum to identify the elemental composition of the sample surface. In some cases, the chemical state of surface atoms can also be determined by the movement of energy and peak shapes.

Auger electrons have relatively low kinetic energy, which limits their depth of flight. Any Auger electrons emitted from an interaction below the surface lose energy through further reaction dispersion along its path towards the surface. Auger electrons emitted at a depth greater than approximately 2 – 3 nm have sufficient energy to escape to the surface and reach the detector. Thus, the volume of analysis for AES only extend to a depth of about 2 nm. Depth of analysis is not influenced by the energy of the primary energy of electrons.

AES instrumentation may include a filament of tungsten or electronic field emission gun electron beam for the primary. The instruments are equipped with secondary electron imaging (SEM) to facilitate the localization of areas of analysis selected, and photographs of the surface of the sample can be obtained. The sample chamber is maintained at ultra vacuum to minimize the interception of Auger electrons by gas molecules between the sample and the detector. Some tools are special tests for the samples to examine the fracture interfaces that have recently been exposed inside the vacuum chamber. A computer is used for the acquisition, analysis and data visualization AES.

INFORMATION ANALYSIS

Survey Scan – The location of the peaks in the spectrum obtained in AES survey scan identifies the elemental composition of the top 20a of the surface analyzed.

Multiplex Scan – The analysis of high resolution Auger spectrum in the region around a peak feature is used to determine the atomic concentration of the elements identified in the scans and in some cases, information on the chemical.

Quantification – The results of AES analysis can be quantified in the absence of rules through the area under the peaks in the spectrum AES and corrections on the basis of elemental sensitivity factors.

Mapping and Line scans – These imaging techniques that measure the lateral distribution of elements on the surface. The electron beam is scanned across the sample surface, or along a fixed line (scan line) or through a designated area (mapping), while the AES signal is analyzed for specific energy channels. The intensity of the AES signal is a function of relative concentration of the element (s) corresponding to the selected channel energy (s). Spatial resolution is approximately 0.3 microns.

Depth profile – the material is removed from the surface by sputtering with an ion beam energy in conjunction with subsequent analysis of AES. This process measures the elemental distribution as a function of depth in the sample. Depth resolution of <100 A is possible.

TYPICAL APPLICATIONS

The identification of microscopic particles
Passive oxide film thickness
Contamination on chips
Quantification of film surface of the light elements
Mapping the spatial distribution of surface constituents

source: actually i get this article from my friend’s blog which unfortunately i forget it’s link, but because of someone claim this article to his mine, so i would credit this article to: www.mee-inc.com, thanks for your claiming, it really helpfull to me and my visitor in order to adding our refference :)

ANALYTICAL INFORMATION

Survey Scan
– The position of the peaks in the AES spectrum obtained in a survey scan identifies the elemental composition of the uppermost 20 Å of the analyzed surface.

Multiplex Scan – A higher resolution analysis of the Auger spectrum in the region around a characteristic peak is used for determination of the atomic concentration of the elements identified in the survey scans and, in some cases, chemical state information.

Quantitation – The AES analysis results can be quantified without standards by using the area under the peaks in the AES spectrum and corrections based on elemental sensitivity factors.

Mapping and Line Scans – These are imaging techniques that measure the lateral distribution of elements on the surface. The electron beam is scanned across the sample surface, either along a fixed line (line scan) or across a given area (mapping) while the AES signal is analyzed for specific energy channels. The AES signal intensity is a function of the relative concentration of the element(s) corresponding to the selected energy channel(s). Spatial resolution is approximately 0.3 µm.

Depth Profile – Material is removed from the surface by sputtering with an energetic ion beam concurrent with successive AES analyses. This process measures the elemental distribution as a function of depth into the sample. Depth resolution of < 100 Å is possible.

TYPICAL APPLICATIONS

Microscopic particle identification
Passive oxide film thickness
Contamination on integrated circuits
Quantitation of light element surface films
Mapping spatial distribution of surface constituents

Tags: Auger Electron Spectroscopy, Auger Electrons, Chemical Composition, Electron Energy, Electronic Field, Elemental Composition, Energy Analysis, Energy Spectrum, Field Emission Gun, Inner Shell, Light Element, Light Elements, Lt 1, Outer Material, Outer Shell, Primary Electron, Primary Energy, Relative Abundance, Surface Atoms, X Rays
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  • kenny gaspar
    11:06 pm on December 2nd, 2010 1

    I need more information about the Auger scanning process. I have a part with surface contamination. Our EDT detector cannot get a reading of this material. The part itself is a cylinder 5.5″ long and 1″ in dia. The contaminated area is in a small recess of .125 inside dia X .125 deep. This recess is a round cylinder and is made of nickel-chrome. My SEM operators believe the cylinder will prevent detection of the contaminant. Any helpful guidance will be accepted
    thanks ken

  • Larry Hanke
    12:13 pm on April 2nd, 2011 2

    Content in this article is very similar to work that I have published on line for several years at http://www.mee-inc.com. I think that credit to the original author is appropriate for this content.

  • techicien
    11:14 am on October 29th, 2011 3

    thanks for your claim :)

 

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